Laser beam shaping for foil-based metallization of solar cells

Abstract

Approaches for foil-based metallization of solar cells and the resulting solar cells are described. For example, a method of fabricating a solar cell involves locating a metal foil above a plurality of alternating N-type and P-type semiconductor regions disposed in or above a substrate. The method also involves laser welding the metal foil to the alternating N-type and P-type semiconductor regions. The method also involves patterning the metal foil by laser ablating through at least a portion of the metal foil at regions in alignment with locations between the alternating N-type and P-type semiconductor regions. The laser welding and the patterning are performed at the same time.

What is claimed is: 
     
       1. A solar cell, comprising:
 a plurality of alternating N-type and P-type semiconductor regions disposed in or above a substrate; and 
 a metal foil welded to the alternating N-type and P-type semiconductor regions by a plurality of welds, the metal foil discontinuous at regions in vertical alignment with locations on a border between adjacent ones of the alternating N-type and P-type semiconductor regions, wherein nearest welds on nearest alternating N-type and P-type semiconductor regions are spaced equally from the corresponding region in vertical alignment with the border between the nearest alternating N-type and P-type semiconductor regions. 
 
     
     
       2. The solar cell of  claim 1 , wherein the metal foil has vertical edges where the metal foil is discontinuous at the border between adjacent ones of the alternating N-type and P-type semiconductor regions. 
     
     
       3. The solar cell of  claim 1 , wherein the plurality of welds is a plurality of laser welds. 
     
     
       4. The solar cell of  claim 1 , wherein the metal foil is an aluminum foil. 
     
     
       5. The solar cell of  claim 1 , wherein the alternating N-type and P-type semiconductor regions are alternating N-type and P-type regions in a polycrystalline silicon layer disposed above the substrate. 
     
     
       6. The solar cell of  claim 1 , wherein the alternating N-type and P-type semiconductor regions are alternating N-type and P-type doped regions in the substrate. 
     
     
       7. A solar cell, comprising:
 a plurality of alternating N-type and P-type semiconductor regions disposed in or above a substrate; 
 a plurality of metal seed material regions on the alternating N-type and P-type semiconductor, the plurality of metal seed material regions discontinuous at regions in vertical alignment with locations on a border between adjacent ones of the alternating N-type and P-type semiconductor regions; and 
 a metal foil on the plurality of metal seed material regions, the metal foil welded to the alternating N-type and P-type semiconductor regions by a plurality of welds through the plurality of metal seed material regions, the metal foil discontinuous at the regions in vertical alignment with the locations on the border between the adjacent ones of the alternating N-type and P-type semiconductor regions, wherein nearest welds on nearest alternating N-type and P-type semiconductor regions are spaced equally from the corresponding region in vertical alignment with the border between the nearest alternating N-type and P-type semiconductor regions, and wherein the metal foil is aligned with the plurality of metal seed material regions. 
 
     
     
       8. The solar cell of  claim 7 , wherein the metal foil and the plurality of metal seed material regions have aligned vertical edges where the metal foil and the plurality of metal seed material regions are discontinuous at the border between adjacent ones of the alternating N-type and P-type semiconductor regions. 
     
     
       9. The solar cell of  claim 8 , wherein the plurality of welds is a plurality of laser welds. 
     
     
       10. The solar cell of  claim 8 , wherein the metal foil is an aluminum foil. 
     
     
       11. The solar cell of  claim 8 , wherein forming the plurality of metal seed material regions comprises aluminum in an amount greater than 97 atomic % and silicon in an amount in the range of 0-2 atomic %. 
     
     
       12. The solar cell of  claim 8 , wherein the alternating N-type and P-type semiconductor regions are alternating N-type and P-type regions in a polycrystalline silicon layer disposed above the substrate. 
     
     
       13. The solar cell of  claim 8 , wherein the alternating N-type and P-type semiconductor regions are alternating N-type and P-type doped regions in the substrate. 
     
     
       14. A solar cell, comprising:
 a plurality of alternating N-type and P-type semiconductor regions disposed in or above a substrate; 
 a trench between each of the alternating N-type and P-type regions, the trenches extending partially into the substrate; 
 a plurality of non-conductive material regions in the trenches; and 
 a metal foil welded to the alternating N-type and P-type semiconductor regions by a plurality of welds, the metal foil discontinuous at regions in vertical alignment with locations on a border between adjacent ones of the alternating N-type and P-type semiconductor regions, and the metal foil overlapping a portion of but not all of the plurality of non-conductive material regions, wherein nearest welds on nearest alternating N-type and P-type semiconductor regions are spaced equally from the corresponding region in vertical alignment with the border between the nearest alternating N-type and P-type semiconductor regions. 
 
     
     
       15. The solar cell of  claim 14 , wherein the metal foil has vertical edges where the metal foil is discontinuous at the border between adjacent ones of the alternating N-type and P-type semiconductor regions. 
     
     
       16. The solar cell of  claim 14 , wherein the plurality of welds is a plurality of laser welds. 
     
     
       17. The solar cell of  claim 14 , wherein the metal foil is an aluminum foil. 
     
     
       18. The solar cell of  claim 14 , wherein the non-conductive material regions are converted paste regions. 
     
     
       19. The solar cell of  claim 14 , wherein the alternating N-type and P-type semiconductor regions are alternating N-type and P-type regions in a polycrystalline silicon layer disposed above the substrate. 
     
     
       20. The solar cell of  claim 14 , wherein the alternating N-type and P-type semiconductor regions are alternating N-type and P-type doped regions in the substrate.